What is the difference between a brass ball valve you get at a department store such as Lowes and a brass ball valve you would find on a Marine Parts website. Below is a link to a couple of lowes valves and a graco valve from wholesalemarine.com. Thanks!

Marine plumbing is bronze, as opposed to just brass. The bronze is less susceptible to salt water and galvanic corrosion, which is not a huge deal with a fresh water trailer boat. Most of the standard plumbing parts are tapered pipe thread, where as marine plumbing can be found with straight threads.

So if you try to connect the valve from lowes to a thru hull intake you will most likely not get a good fit and could leak. That sounds like a good reason to go with the marine valves, i just wanted to know why i will be paying double before i installed my ballast system. Thanks for the input!

I've read a lot of Compass Marine's articles, and he has a bit to say about using inexpensive Brass valves here (read down a few pages). Of course, he's mostly discussing salt-water cruising, so his opinions may not directly apply to your situation.

What about threading the tsunami pump into the valve? I looked at the 1200 gpm pump with the 1 inch inlet and the threads were tapered.

The Attwood Tsunami 4663-7 with its 1" NPT is best suited to screw right on top of the ball-valve. If bilge depth is an issue, then use a 90* elbow. This gets the pump vertical, but make sure the pump's outlet is oriented up. Another option is to use a pump like the Rule 1100, which is actually faster in a real world test, and .75" thru-hull and ball-valve. Even though this pump cost more, the price difference between the .75" thru-hull and B/V and the 1" bronze closes the gap. Both the T1200 and the Rule 1100 use a 1.125" outlet, so the same 1" hose can be fitted.